Re: [boost] [MPL.Math] Updated version now available

From: Cromwell Enage (sponage_at_[hidden])
Date: 2005-12-30 00:10:51

--- Andy Little wrote:
> Hi Cromwell,

Hey, Andy.

> > Registration of each metafunction occurs at the
end of the
> > header file in which the metafunction is declared,
as per the
> > "don't pay for what you don't use" policy.
> 
> Thats great and suits me, but I was wondering
whether it might
> be better to really make this optional, either by
looking for a
> macro BOOST_TYPEOF_PLEASE_REGISTER_MY_INCLUDED_TYPES
(or
> whatever name) or by putting the typeof stuff in a
separate
> include file.

The macro route is probably better.

> Point is that on some compilers where there is no
inbuilt
> typeof, then Boost.Typeof causes a big slow down in
> compile-performance.  AFAIK this happens in VC8,
though I
> haven't tried this compiler myself so I'm only
guessing.

You can #define BOOST_TYPEOF_COMPLIANT to force
emulation mode, so you don't have to guess.

> [..]
> I would question the name 'inverse' to replace
'reciprocal',
> because it needs a function to take the inverse of,
whereas
> reciprocal is unequivocal:

Okay.  It's probably better than
'multiplicative_inverse' as well.  OTOH, we'd also
break a long-standing tradition of using ambiguous
names for certain mathematical functions.  :)

> FWIW I have attached some other related functions
that might be
> useful.
> 
> boost::mpl::math::is_positive<T>, to go with 
> boost::mpl::math::is_negative<T>
> boost::mpl::math::is_rational_constant<T>, to go
with
> boost::mpl::is_integral_constant<T>
> boost::mpl:rational_int<>
> boost::mpl:rational_long<>

is_positive<> is okay, as long as
is_strictly_positive<> (which zero<> is not) goes with
it.  I'd like to know how your Physical Quantities
library uses the other metafunctions, so I can see if
there are more generic ways to facilitate such usage
(e.g. for seamless interaction with double_c).

> Finally regarding the boost::mpl::math::power
function, I was
> told once upon a time that the traditional way to do
this in mpl
> would be to call it just 'pow' after the runtime
version. FWIW

No one told me.  I just thought using full names was
more readable (and educational, too; I didn't know
"asin" stood for "arcus sine" until Peder Holt used
that name).

                              Cromwell D. Enage

        
                
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